Lecture 4: Actuators and Sensors

Question 1

What are 3 robot components? Briefly explain them.

Answer 1

Physical body, sensors, effectors, controllers (any 3)

Physical body is the embodiment in the world.

Sensors are used to sense the environment.

Effectors are used to take actions.

Controllers are used to be autonomous and have goals.

Question 2

What are examples of effectors?

Answer 2

Legs, wheels, fingers

Question 3

What is the difference between an effector and actuator? How are they related?

Answer 3

An effector is any device that has an effect on the environment, but an actuator is a mechanism enabling the effector to execute movement. For example, the legs are effectors, but the muscles and joints are actuators.

An effector needs at least one actuator.

Question 4

A joint is an ______ connecting two ____ ____.

Answer 4

actuator, body, parts

Question 5

What are DoFs? What are the two types of DoFs?

Answer 5

Degree of Freedom is the dimension of movement. The two types are translational DOF (x, y, z without rotation) and rotational DOF (Roll, Pitch, Yaw).

Question 6

Match each term to the correct statement:
1. Holonomic
2. Non-holonomic
3. Redundant

A. C.DOF < T.DOF
B. C.DOF > T.DOF
C. C.DOF = T.DOF

Answer 6

1 C
2 A
3 B

Question 7

How many DOFs in the human-arm?

Answer 7

7 total: 3 shoulder, 1 elbow, 3 wrist

Question 8

True of False: Two joints can share the same actuator.

Answer 8

False. Each joint needs a separate actuator.

Question 9

Explain the difference between active actuators and passive effectors.

Answer 9

Active actuator uses energy to provide power to move the effector.

Passive effector uses passive actuation mechanisms exploiting the body-environment physics interaction.

Question 10

Give an example of a passive effector.

Answer 10

A leg that uses passive joints. For example, when walking up a slope, the joints apply more pressure subconciously.

Question 11

Which historical robotics theory exploits passive effectors?

Answer 11

Pfeifer’s embodied intelligence

Question 12

What is Pfeifer’s embodied intelligence?

Answer 12

A theory that emphasizes that the body is intelligent if it exploits the body-brain-environment relationship.

Question 13

What is morphological computation?

Answer 13

Morphological computation refers to the process where the computation for the movement is implicitly off-loaded to the body and its existence in the environment.

Question 14

What are two types of actuators? (not passive/active but examples)

Answer 14

Electric motors
Hydraulics
Pneumatics
Reactive materials

(any 2 are correct)

Question 15

Sensors are physical devices to measure ____ _____.

Answer 15

physical quantities

Question 16

Give an example of an internal sensor and external sensor.

Answer 16

Internal sensor: battery, motor
External sensor: vision, distance

Question 17

Why can a robot have sensor uncertainty? Give three possible reasons.

Answer 17

Sensor noise and errors
Sensor limitations
Sensor calibration
Lack of prior knowledge about environment

Question 18

Match each level of sensory processing to the correct term:

1. Low
2. Medium
3. High

A. Electronics
B. Computation
C. Signal processing

Answer 18

1 A
2 C
3 B

Question 19

What are the two perception theories?

Answer 19

The first is passive vision which is the robot passively observing (bottom-up).

The second is active vision where the robot uses knowledge about a task to look for particular stimuli

Question 20

Briefly explain two types (examples) of sensors.

Answer 20

SLAM is used for position and localisation.

Sonars use sound for navigation and ranging.

LIDARs use light for navigation and ranging.